Background Propofol is considered the drug of anesthetic induction par excellence, due to its fast onset and short duration of action, easy titration and positive profile for side effects. However, between 30% and 80% of the patients experience pain on injection of Propofol, being this the seventh disadvantage among the most important ones within the current anesthetic practice
Objective Evaluate and compare the effectiveness of diluted Propofol at 0.5%, vs. the Modified Bier Block to decrease the pain produced by the application of Propofol during anesthetic induction in adult patients.
Design A prospective, controlled, randomized and double-blind clinic experiment was conducted in adult population between 18 and 60 years, who were taken to surgery under general anesthesia in Fundación Cardioinfantil and induced with Propofol. The patients were randomly divided in three groups: Group 1, Propofol at 1%; Group 2, Propofol at 0.5%; and Group 3, Modified Bier block
Results A total of 68 patients were included in the clinical study, in which two patients were excluded due to difficult venous access and the use of a intravascular catheter 20G size that was out of the standard protocol. It was found a higher frequency of patients that reported no pain with the infusion of Propofol in group 3, in which the modified Bier block was applied, compared with the other two groups: 73,9% in group 3 vs. 27,3% and 19% in group 1 and 2 respectively.
Conclusion Propofol at a 0,5% concentration, diluted with normal saline solution or Ringer´s lactate, is not effective to decrease pain during the drug administration, compared to Propofol at 1% and the modified Bier block, which is the gold standard regarding pain reliever.

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